This section provides background information related to the present disclosure which is not necessarily prior art.
An internal combustion engine may use a turbocharger to increase density of air and consequently the amount of air that enters the engine. The increased amount of air enables more fuel to be injected into the engine, thereby increasing engine power. A turbocharger generally includes a turbine, an air compressor, and a shaft that connects the turbine to the air compressor. The turbine is driven by exhaust gas that flows from an exhaust manifold. The air compressor is driven by the turbine to compress the air that enters an intake manifold.
High-efficiency turbochargers can employ variable geometry systems to increase performance and efficiency. Conventional variable geometry turbines can include a variable geometry element such as a set of movable vanes or a nozzle ring that are used to control pressure of the exhaust gas flowing through the turbine. The flow of exhaust gas is low at low engine speeds. In the case of a movable vane system, the movable vanes direct the trajectory of the exhaust gas approaching the blades of the rotating turbine wheel, so as to vary the change in momentum of the gas as it passes the turbine wheel. Varying the torque imparted to the wheel, varies the rotating speed of the turbine wheel. An indirect effect of varying the vane angle and change in work is the change in turbine inlet pressure at a given flow rate.
In the case of a movable nozzle ring, the ring is movable concentric with the axis of rotation of the turbine to reduce or increase the area of the nozzle inlet in order to optimize the turbine's efficiency based upon the engine sped.
Variable geometry turbines generally include an actuator for varying the geometry of the turbine system. The actuator system can include an electromechanical actuator or servomotor that is drivingly connected to an actuator shaft or arm that passes through the turbocharger housing for adjusting the variable geometry turbine. Due to the high temperature of the turbine housing, shaft seals are incapable of adequately sealing around the actuator shaft without durability concerns.
Accordingly, an internal combustion engine is provided with a turbocharger with a variable geometry turbine having an actuator shaft or arm passing through the turbocharger housing. The actuator shaft opening is vented to the engine crankcase for diverting exhaust that passes through the actuator shaft opening to the crankcase.
Further areas of applicability will become apparent from the description provided herein. The description and specific examples in this summary are intended for purposes of illustration only and are not intended to limit the scope of the present disclosure.
Corresponding reference numerals indicate corresponding parts throughout the several views of the drawings.